68 L-68 tripower correct sparks plugs

[Joseph C.]

Does anyone know the correct spark plugs for 68 L-68 tripower. I was told 43n's or 44's??
Thanks

Joe Clarino
68 L-68 conv
66 Coupe

[Dick W.]

Re: 68 L-68 tripower correct sparks plugs

45's will run better for average street driving. Less fouling

[Joseph C.]

Re: 68 L-68 tripower correct sparks plugs

Are they correct for judging?

[Wayne M.]

Re: 68 L-68 tripower correct sparks plugs

Are they correct for judging?

Joe -- the GM Engine Tune-up Charts show, for 1968 models, the standard plug as AC43N, with the cold service plug as AC42N. That's for ALL Mk IV motors (396 and 427) and all horsepower ratings (exc. L88, which were AC43XL and AC42XL, respectively).

So I would expect that the judging manuals would reflect the presence of the standard plug. Agree with Dick that AC45N would be better for non-judging purposes.

[Joseph C.]

Re: 68 L-68 tripower correct sparks plugs

thank you for replying

[Jeffrey S.]

Re: 68 L-68 tripower correct sparks plugs

Joe:
The plug that was in your engine and all big block engines except L-88 and L-89 through 1968 were AC43N (R43N's were used in 1969 production). As I understand it, only Bloomington judging requires that exact plug. NCRS only requires that an AC plug be in the car and a note might be made if it can be determined that a plug other than the assembly line plug is in the car. Others who are far more experienxced than me might have more on the judging aspect.
Jeff

[Dick W.]

Re: 68 L-68 tripower correct sparks plugs

It is almost impossible to read the part number on the plug when installed. The boots usually cover the #'s up. I just look for the green ring on the ceramic insulator.

[Paul H.]

Re: 68 L-68 tripower correct sparks plugs

45's will run better for average street driving. Less fouling

I agree. I am running R45 XLS in my 68 L36 and it runs great. I like 5 range plugs in both small and big blocks for all around street driving.